Spinel LiNi0.5Mn1.5O4 with ultra-thin Al2O3 coating for Li-ion batteries: investigation of improved cycling performance at elevated temperature

In this study, spinel LiNi_0.5Mn_1.5O₄ (LNMO) was successfully decorated with Al₂O₃ thin film by using atomic layer deposition (ALD) approach and evaluated as a cathode material for high-temperature applications in lithium ion batteries (LIBs). To optimize the LNMO-Al₂O₃ electrodes operated at elevated temperature (55 °C), the effects of Al₂O₃ thicknesses adjusted by controlling the ALD deposition cycle were systemically investigated. According to the series of electrochemical results, the LNMO coated with the Al₂O₃ thin layer in the thickness of ca. 2 nm was achieved by using one-cycle ALD and the LNMO-Al₂O₃ electrode exhibited superior electrochemical stability (capacity retention up to 93.7% after consecutive 150 charge/discharge cycles at 0.5 C to the pristine LNMO electrode at elevated temperature. This can be attributed to two factors: (i) the decoration of Al₂O₃ thin layer could not contribute remarkably to extra resistance for charge transfer; (ii) Al₂O₃ thin film deposition could efficiently stabilize the growth of cathode electrolyte interface (CEI) and suppress the dissolution of transition metals. Therefore, these results verify that the LNMO-Al₂O₃ electrode could be regarded as a promising cathode material for high-voltage LIBs, especially at elevated temperature operation.